1. Field of the Invention
The present invention concerns a process for producing rice vinegar by forming a saccharified liquid from rice as the starting material and applying alcoholic fermentation, or by directly applying alcoholic fermentation to the starting rice by way of an enzymatic non-cooking process, and then applying acetic acid fermentation with acetic acid bacteria.
2. Description of the Prior Art
Rice vinegar has long been used as a sour seasoning and has been generally favored in cooking for Sushi or the like.
The process for producing rice vinegar known so far has been conducted by processing rice as the starting material, applying alcoholic fermentation, denaturing the resultant MOROMI (fermentation product) with brewed vinegar, then removing KASU (residue), leaving the product for a predetermined of period, removing ORI (precipitates) and applying acetic acid fermentation by the aerated stirring process to the resultant liquor material (refer, for example, to Japanese Patent Publication No. Sho 57-5510).
There has also been known a process for producing vinegar by applying alcoholic fermentation to non-cooked cereals or processed cereals while adding malt (=koji), enzyme and vinegar or acetic acid and then applying acetic acid fermentation (refer, for example, to Japanese Patent Laid-Open No. Sho 61-11913).
The production processes in the prior art as described above have a drawback of causing so-called stuffy odors, since there have often been contamination risks with miscellaneous bacteria upon alcoholic fermentation, acetic fermentation or during storage. Lactic acid is formed, for example, due to the contamination with lactic acid bacteria in alcoholic fermentation and is converted into acetoin or diacetyl upon acetic acid fermentation or during storage, to cause so-called stuffy odors.
In the conventional rice vinegar production process described above, the brewing step and the temperature of the alcoholic fermentation are controlled so that no rancidity or other contamination may be caused and acetic acid fermentation is carried out after removing residues or precipitates introduced from MOROMI after the completion of the alcoholic fermentation. However, these procedures have not yet completely solved the foregoing problems.
In addition, in the conventional vinegar production process as described above, there have been attempts to suppress the generation of lactic acid bacteria by conducting non-cooked alcoholic fermentation at 20-35 .degree. C. while adding vinegar or acetic acid, thereby reducing the formation of lactic acid which forms a precursor of undesired odors referred to as stuffy odors during acetic acid fermentation. However, since the peculiar odors in vinegar are derived not only from such stuffy odors but also from nitrogen compounds derived from the starting material, no complete solution have yet been obtained.